1. Field of the Invention
The present invention relates to torque limiting clutches and in particular to a detent device for limiting the torque applied to the clutch in a vacuum cleaner rotating brush.
2. Description of the Prior Art
The present invention is useful in an upright vacuum sweeper which has a floor engagable brush dowel rotatably driven by a cog belt which engages a sprocket carried on the brush dowel. If the brush dowel becomes jammed such as by engagement with a sock or other article, a clutch mechanism permits the sprocket to slip with respect to the brush dowel to prevent damage to the cog belt. The vacuum sweeper includes a control circuit such as that disclosed in U.S. Pat. No. 4,370,690 to terminate operation of the motor driving the brush dowel in the event the sensed speed of the brush drops below a predetermined low speed.
However, if the control circuit were to fail, and then the brush dowel is jammed, the motor will not turn off. It would be desirable to prevent heat generated by friction within the clutch from reaching excessive temperatures. Since the brush dowel is oftentimes constructed of wood, any excessive heat could cause the wood to char or ignite.
Various types of clutches have been suggested in prior patents for driving a rotary brush in a vacuum cleaner. In U.S. Pat. No. 3,757,382 it is disclosed to use a pulley on the brush roller which has high and low friction areas so that the amount of friction of the driven pulley will be reduced relative to the friction of the drive pulley in order to enhance a slippage under overload conditions.
U.S. Pat. No. 4,317,253 discloses an override clutch device which has a spring member with a deformable end which is to be in contact with a boss on the driven pulley which will deform to permit the pulley to rotate relative to a jammed brush roller.
U.S. Pat. No. 4,532,667 discloses a clutch mechanism for connecting a brush assembly to a driven pulley which comprises a S-shaped spring having ends which engage with recesses in the interior of the pulley but which can be deformed away from the recesses upon the occurrence of a jammed brush.